Variable resistance memory device and method of manufacturing the same

ABSTRACT

A variable resistance memory device includes a semiconductor substrate having a vertical transistor with a shunt gate that increases an area of a gate of the vertical transistor.

CROSS-REFERENCES TO RELATED APPLICATION

This application is a division of U.S. patent application Ser. No.13/795,872 filed on Mar. 21, 2013 now U.S. Pat. No. 8,981,448 B2, whichclaims priority under 35 U.S.C. 119(a) to Korean application number10-2012-0146380, filed on Dec. 14, 2012, in the Korean Patent Office.The disclosure of each of the foregoing application is incorporated byreference in its entirety.

BACKGROUND

1. Technical Field

The inventive concept relates to a variable resistance memory device anda method of manufacturing the same, and more particularly, to a variableresistance memory device and a method of manufacturing the same using atransistor as an access device.

2. Related Art

Nonvolatile memory devices have characteristics that data stored thereinis not erased even in power off and thus the nonvolatile memory deviceshave been widely adopted by computers, mobile telecommunication systems,memory cards, and the like.

Flash memory devices have typically been widely used as the nonvolatilememory devices. The flash memory devices typically have memory cellshaving a stack gate structure. To improve reliability and programefficiency in the flash memory devices, film quality of a tunnel oxidelayer has to be improved and a coupling ratio of a cell has to beincreased.

Currently, next-generation memory devices, for example, phase-changerandom access memories (PCRAMs), resistance RAMs (ReRAMs), andmagentoresistive RAMs (MRAMs) have been suggested.

As typical next-generation memory devices, PCRAMs need an access deviceconfigured to selectively provide current to a phase-change resistancelayer. Currently, transistors and diodes are mainly used as the accessdevice in the PCRAMs.

However, the transistors have a low threshold voltage, but thetransistors occupy a relatively larger area than the diodes. While thediodes occupy a smaller area than the transistors, the diodes have alarger threshold voltage than the transistors. Further, if the diodesare arranged over a word line, then word line bouncing may be caused dueto a resistance difference of the cord line according to an arrangementposition of the diodes.

SUMMARY

According to one aspect of an exemplary embodiment, there is provided avariable resistance memory device. The variable resistance memory devicemay include: a semiconductor substrate; a plurality of verticaltransistors arranged at a fixed interval on the semiconductor substrate;a variable resistive region formed on each of the plurality of verticaltransistors; and a shunt gate disposed in a space between adjacentvertical transistors and configured to be electrically connected to agate of each of the plurality of vertical transistors.

According to another aspect of an exemplary embodiment, there isprovided a method of manufacturing a variable resistance memory device.The method may include: forming a plurality of vertical transistors on asemiconductor substrate, each of the plurality of vertical transistorsincluding a pillar and a gate surrounding a lower portion of the pillar;forming a first spacer and a second spacer on a sidewall of the pillaron the gate; burying an insulating layer between the verticaltransistors; removing the second spacer disposed on one side of thepillar and an upper portion of the insulating layer to define a space;and burying a conductive material in the space to form a shunt gate.

According to another aspect of an exemplary embodiment, there isprovided a semiconductor memory device. The semiconductor memory devicemay include: gates each surrounding channel pillars; and a shunt gatedisposed between the channel pillars and configured to be connected oneof adjacent gates to extend an area of the gate.

These and other features, aspects, and embodiments are described belowin the section entitled “DETAILED DESCRIPTION”.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thesubject matter of the present disclosure will be more clearly understoodfrom the following detailed description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a plan view illustrating an arrangement of channel pillarsaccording to an exemplary embodiment;

FIGS. 2A and 2B, FIGS. 3A and 3B, FIGS. 4A and 4B, FIGS. 5A and 5B,FIGS. 6A and 6B, FIGS. 7A and 7B, and FIGS. 8A and 8B arecross-sectional views illustrating a method of manufacturing anexemplary variable resistance memory device; and

FIGS. 9 and 10 are cross-sectional views illustrating exemplary variableresistance memory devices.

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments will be described in greater detailwith reference to the accompanying drawings.

Exemplary embodiments are described herein with reference tocross-sectional illustrations that are schematic illustrations ofexemplary embodiments (and intermediate structures). As such, variationsfrom the shapes of the illustrations as a result, for example, ofmanufacturing techniques and/or tolerances, are to be expected. Thus,exemplary embodiments should not be construed as limited to theparticular shapes of regions illustrated herein but may be to includedeviations in shapes that result, for example, from manufacturing. Inthe drawings, lengths and sizes of layers and regions may be exaggeratedfor clarity. Like reference numerals in the drawings denote likeelements. It is also understood that when a layer is referred to asbeing “on” another layer or substrate, it can be directly on the otheror substrate, or intervening layers may also be present.

FIG. 1 is a plan view illustrating an arrangement of channel pillarsaccording to an exemplary embodiment. FIGS. 2A and 2B, FIGS. 3A and 3B,FIGS. 4A and 4B, FIGS. 5A and 5B, FIGS. 6A and 6B, FIGS. 7A and 7B, andFIGS. 8A and 8B are cross-sectional views illustrating a method ofmanufacturing an variable resistance memory device. FIGS. 2A, 3A, 4A,5A, 6A, 7A, and 8A are cross-sectional views taken along line a-a′ (adirection parallel to a word line) of FIG. 1 and FIGS. 2B, 3B, 4B, 5B,6B, 7B, and 8B are cross-sectional views taken along line b-b′ (adirection parallel to a bit line) of FIG. 1.

Referring to FIGS. 1, 2A, and 2B, a portion of a semiconductor substrate100 is etched to form pillars 100 a. The pillars 100 a may be, disposedin a matrix as illustrated in FIG. 1. An upper region of each of thepillars 100 a becomes a drain region, the semiconductor substrate 100,connecting each of the pillars 100 a, becomes a common source region ofan access device, and a portion of each of the pillars 100 a, betweenthe drain region and the common source, becomes a channel region of theaccess device. The drain region and the common source region may beformed and defined through a separate impurity implantation process.

A first insulating layer 110 is deposited on surfaces of the pillars 100a and the semiconductor substrate 100 and then a second insulating layer115 may be formed in a space between the pillars 100 a. The secondinsulating layer 115 is anisotropically over-etched to remain only in alower portion of the space between each of the pillars 100 a. The secondinsulating layer 115, remaining in the space between the pillars 100 a,may define a height of a main gate to be formed later. At this time, thefirst insulating layer 110 and the second insulating layer 115 on anupper surface of each pillar 100 a may be removed through theanisotropic etching process of the second insulating layer 115.

Referring to FIGS. 3A and 3B, a first spacer 120 and a second spacer 125are formed on a side of the first insulating layer 110, which is formedon a sidewall of each of the pillars 100 a. The first spacer 120 and thesecond spacer 125 may include an insulating layer and may be formedsequentially or simultaneously. Here, the first spacer 120 serves toprotect the first insulating layer 110 surrounding each of the pillars100 a and the second spacer 125 may be a sacrificial layer for defininga shunt gate to be formed later. The first spacer 120 and the secondspacer 125 may be formed of a material having an etch selectivity thatis higher than an etch selectivity of the material that forms the secondinsulating layer 115.

Referring to FIGS. 4a and 4B, the second insulating layer 115, exposedby the first spacer 120 and the second spacer 125 is selectivelyremoved. A wet etch method may be used to selectively remove the secondinsulating layer 115. By removing the second insulating layer 115, asidewall of a lower portion of each of the pillars 100 a and a surfaceof the semiconductor substrate 100 is exposed.

Next, a gate insulating layer 130 is formed along the exposed sidewallof each of the pillars 100 a and the exposed surface of thesemiconductor substrate 100 and a gate electrode material is formedwithin a spacer surrounded by the gate insulating layer 130. Forexample, the gate electrode material may include a metal, such asselected from the group consisting of tungsten (W), copper (Cu),titanium nitride (TiN), tantalum nitride (TaN), tungsten nitride (WN),molybdenum nitride (MoN) niobium nitride (NbN), titanium silicon nitride(TiSiN), titanium aluminum nitride (TiAlN), titanium boron nitride(TiBN), zirconium silicon nitride (ZrSiN), tungsten silicon nitride(WSiN), tungsten boron nitride (WBN), zirconium aluminum nitride(ZrAlN), molybdenum silicon nitride (MoSiN), molybdenum aluminum nitride(MoAlN), tantalum silicon nitride (TaSiN) tantalum aluminum nitride(TaAlN), titanium (Ti), molybdenum (Mo), tantalum (Ta), titaniumsilicide (TiSi), titanium tungsten (TiW), titanium oxynitride (TiON),titanium aluminum oxynitride (TiAlON), tungsten oxynitride (WON), ortantalum oxynitride (TaON). Alternatively, the gate electrode materialmay include a semiconductor, such as doped polysilicon or silicongermanium (SiGe).

Next, the gate electrode material and the gate insulating layer 130 arepatterned using the second spacer 125 as a mask to define a main gate(or surround gate) 135. In FIG. 4A, H1 is a space between main gates 135when viewed in a word line direction.

Referring to FIGS. 5A and 56, a third insulating layer 140 is buried inthe space H1 between the gate electrodes 135. A tilted ion implantationprocess is performed to implant impurity ions into the second spacer125, which is formed perpendicular to the semiconductor substrate 100.The tilted ion implantation process uses various ions, such as argon(Ar) ion and hydrogen (H), and damages the second spacer 125. At thistime, an upper region of the third insulating layer 140 is also damagedby the tilted ion implantation process.

Referring to FIGS. 6A and 6B, the second spacer 125 and the thirdinsulating layer 140, which have been damaged by the tilted ionimplantation process, are selectively removed to define a shunt gateformation region H2. As is generally known, an etch rate in a materialmay be varied according to a degree of damage by ion implantation. Inthe exemplary embodiment, the damaged second spacer 125 and the damagedportion of the third insulating layer 140 are selectively removed basedon the degree of damage to define a shunt gate formation region H2. Theshunt gate formation region H2 exposes the main gate 135. The referencenumeral 140 a denotes a remaining third insulating layer.

Referring to FIGS. 7A and 7B, a conductive material is provided in theshunt gate formation region H2 to form a shunt gate 145 that is incontact with the main gate. The conductive material may include, forexample, W, Cu, TiN, TaN, WN, MoN, NbN, TiSiN, TiAlN, TiBN, ZrSiN, WSiN,WBN, ZrAlN, MoSiN, MoAlN, TaSiN, TaAlN, Ti, Mo, Ta, TiSi, TiW, TiON,TiAlON, WON, or TaON. Alternatively, the conductive material may includea semiconductor, such as doped polysilicon layer or silicon germanium(SiGe). The shunt gate 145 is electrically connected to the main gate135 to extend an area of the main gate 135 and thus, reduce total gateresistance.

Referring to FIGS. 8A and 8B, an interlayer insulating layer 150 isformed on the semiconductor substrate on which the shunt gate 145 isformed and then etched to expose each of the pillars 100 a. Therefore, avariable resistive region PCA is defined. A heating electrode 155 isformed in a lower portion of the variable resistive region PCA through aconventional method. A heat-endurance spacer 160 is formed on a sidewallof the variable resistive region PCA. A variable resistive layer 165 isformed in the variable resistive region PCA. At this time, the variableresistive layer 165 may include a PCMO layer, which is a material for aReRAM, a chalcogenide layer, which is a material for a PCRAM, a magneticlayer, which is a material for a MRAM, a magnetization reversal devicelayer, which is a material for a spin-transfer torque magnetoresistiveRAM (STTMRAM) or a polymer layer, which is a material for a polymer RAM(PoRAM). A bit line 170 is formed on the semiconductor substrateincluding the variable resistive layer 165.

According to the exemplary embodiment, the variable resistance memorydevice uses a vertical transistor, having a surround gate structuresurrounding a pillar, as an access device to provide a low thresholdvoltage and to reduce an area of the access device as compared with atransistor in the related art.

Further, the shunt gate connected to the surround gate is formed in thespace between the pillars so that a gate area is increased to reducegate resistance and word line resistance is improved to reduce word linebouncing.

The shunt gates are disposed with the pillar, the first insulating layer110, and the first spacer 120 interposed therebetween to have asufficient insulating layer thickness. Therefore, capacitancecharacteristic can be also improved and the word line bouncing can befurther reduced.

As illustrated in FIG. 9, a first portion 145 a-1 of a shunt gate and asecond portion 145 a-2 of the shunt gate may be formed to extend betweenvariable resistive regions PCA. The first portion 145 a-1 of the shuntgate extends in a space between each of the pillars 100 a, and thesecond portion 145 a-2 of the shunt gate extends in a space betweenvariable resistive layers 165. Thus, the second portion 145 a-2 of theshunt gate is entirely disposed between variable resistive layers 165.Moreover, the second portion 145 a-2 of the shunt gate is wider than thefirst portion 145 a-1 of the shunt gate in a direction parallel to thesurface of the substrate. According to the exemplary embodiment, an areaof a gate electrode can be increased by the first portion 145 a-1 of theshunt gate and the second portion 145 a-2 of the shunt gate.

As illustrated in FIG. 10, a first portion 145 a of a shunt gate asecond portion 145 b of the shunt gate may be formed to extend betweenvariable resistive regions PCA, The first portion 145 a of the shuntgate extends in a space between each of the pillars 100 a, and thesecond portion 145 b of the shunt gate extends in a space between eachof the pillars 100 a and between the variable resistive layers 165.Moreover, the second portion 145 b of the shunt gate is wider than thefirst portion 145 a of the shunt gate in a direction parallel to thesurface of the substrate. According to the exemplary embodiment, an areaof a gate electrode can be increased by the first portion 145 a-1 of theshunt gate and the second portion 145 a-2 of the shunt gate.

After the shunt gate 145 is formed as in the exemplary embodiment, theportion of the shunt gate disposed between the variable resistive layers165 may be formed by forming an additional conductive layer andpatterning the additional conductive layer to be electrically connectedto the shunt gate 145, so that the extending shunt gates 145 a-1 and 145a-2 and 145 a and 145 b may be formed. Here, the reference numeral 146is a hard mask for defining the shunt gate disposed between the variableresistive layers 165 and the reference numeral 170 denotes a bit line.

The above exemplary embodiment is illustrative and not imitative.Various alternatives and equivalents are possible. The invention is notlimited by the embodiment described herein. Nor is the invention limitedto any specific type of semiconductor device. Other additions,subtractions, or modifications are obvious in view of the presentdisclosure and are intended to fall within the scope of the appendedclaims.

What is claimed is:
 1. A method of manufacturing a variable resistancememory device, the method comprising: forming a plurality of verticaltransistors extending from a surface of a semiconductor substrate in adirection perpendicular to the length and the width of the semiconductorsubstrate, each of the plurality of vertical transistors including apillar and a gate surrounding a lower portion of the pillar; forming afirst spacer and a second spacer on a side wall of the pillar; formingan insulating layer between the plurality of vertical transistors;defining a space by removing the second spacer and an upper portion ofthe insulating layer; and providing a conductive material in the spaceto form a shunt gate.
 2. The method of claim 1, further comprising:forming, between the shunt gates, a heating electrode on each of thevertical transistors; and forming a variable resistive layer on theheating electrode.
 3. The method of claim 1, wherein the defining aspace further comprises: damaging the second spacer and the upperportion of the insulating layer; and selectively removing the secondspacer and the upper portion of the insulating layer.
 4. The method ofclaim 3, wherein the second spacer and the upper portion of theinsulating layer are damaged via a tilted ion implantation process. 5.The method of claim 1, further comprising: depositing a conductive layeron the semiconductor substrate and the shunt gate; patterning theconductive layer to form a shunt gate extension, connected to the shuntgate, in the space between the vertical transistors; and forming aheating electrode and a variable resistive layer on each of verticaltransistors at both sides of the shunt gate extension.
 6. The method ofclaim 5, further comprising: forming an additional gate layer on theshunt gate; and forming a variable resistive structure on each of thevertical transistors.
 7. The method of claim 6, wherein the forming thevariable resistive structure includes: forming a heating electrode oneach of the vertical transistors; and forming a variable resistivematerial layer on the heating electrode.